Harbors and other waterfront and off-shore structures are vulnerable to attack by small watercraft, i.e., vehicles, vessels or crafts that move across or through water, such as a speedboat. These watercraft are common in the water and are used for many purposes such as for pleasure, recreation, physical exercise, commerce, transport of people, and goods. It is difficult to distinguish recreational watercraft from a hostile watercraft, such as, a watercraft loaded with explosives that is designed to detonate and cause harm to people, structures, and other watercraft. A small hostile watercraft can potentially slip into a harbor or other waterfront structure unnoticed or otherwise undeterred and cause severe damage to people and property.
Near shore, port, and off-shore barriers are known. Examples of such barriers are described in U.S. Pat. Nos. 4,135,467, 6,681,709, and 6,843,197. These barriers consist of low freeboard float lines or log booms that mark a restricted area, or higher freeboard barriers fabricated of molded plastic or inflated rubber tubes. A port security barrier (PSB) comprised of continuous modular, floating barrier that is installed in lengths ranging from a few hundred feet to over a mile is also known. Each PSB module of the PSB system includes a capture net fabricated from nylon or other synthetic line and net support structure which operates to stop the waterborne craft and prevent entry into the port. However, these barriers suffer from one or more of the disadvantages of being ineffective against higher speed watercraft, are floating and subject to below water level threats such as swimmers, divers, and torpedoes, have unsuitable damage from the impact of a watercraft, have high maintenance costs, and/or are unreliable in the wind, waves, currents, storms and other harsh environmental conditions at sea.
Therefore, there is a need for a barrier system that is effective against high speed watercraft, can provide protection from subsurface threats, is resistant to environmental energies and damage from attacking watercraft, and has lower maintenance costs.